function destruyeSesion()
{
    createWaiting();
    $.ajax
            ({
                type: "POST",
                url: "./php_sesion_destroy.php",
                data:
                        {
                            req: "sesion_destroy"
                        },
                success: function(data)
                {
                    var json = jQuery.parseJSON(data);
                    user = json.user;
                    doc.getElementById("us").innerHTML = "";
                    doc.getElementById("lg").innerHTML = "<img src = 'imagenes/login.png'> <b>Iniciar Sesión</b>";
                    tipoUser = "";
                    logged = json.success;
                    helps = null;
                    backInicio();
                    closeWaiting();
                }
            });
    return false;
}